If there’s one thing you can be sure about in the NFL, it’s that nothing is a sure thing.

The spiraling Steelers, coming off a defensive collapse in which they allowed a franchise-worst 55 points to New England, slam down the Steel Curtain the next week on Buffalo.

Defending Super Bowl champion Baltimore follows three tight losses, in which it shows little resilience and no finishing touch, by winning in overtime against Cincinnati — after allowing a last-second desperation TD pass at the end of regulation.

Clubs that look good in Week 9, such as the Titans, Redskins and Bears, fall flat in Week 10.

Hey, even the Jaguars win after eight flops.

Not long ago, the Panthers were considered a contender with Tampa Bay for the basement in the AFC South. Now, they have won five straight and might just win the division.

The Giants opened the season with six losses, convincing their fans the sky was falling on the Jersey Meadowlands. Now they’ve won three in a row and — get this — are a contender in the awful NFC East.

The only true trend in pro football is that there is no such thing as a true trend.

“You win and lose as a team, and that’s the only common thread,” Bill Parcells said last summer when he was inducted into the Hall of Fame. “Every week, every game, is a separate thing, a separate entity. Even if you have won a whole bunch (in a row) or lost a whole bunch, it doesn’t mean there’s a tendency to have the same things happen again.”

Inconsistency is the bane of all coaches and, by extension, their players. They all are creatures of habit, so much so that looking beyond the upcoming game and opponent is a recipe for failure.

Yet they can’t seem to string together solid performances; other than a handful of teams this year — Kansas City, Denver and Seattle — who has found any consistency in a positive way?

Perhaps the best examples of the unpredictability running rampant throughout the NFL are the Jets and Cowboys.

Rex Ryan’s club should be pleased with its 5-4 mark as it comes off its bye, considering where New York was projected to finish. Yet it is maddening to the Jets that they have alternated wins and losses each week, tying an NFL mark through nine games.

Even wilder, they can go from losing to winless Pittsburgh to beating archrival New England to getting blown out by Cincinnati to outplaying New Orleans in the last month.

“You want to find that consistency where you are able to get things going and keep them going,” Ryan says. “We’re always searching for that.”

With a young roster on a rebuilding team, steadiness is particularly elusive. The Jets have a solid defense, Ryan’s coaching strength, but it was annihilated by the Bengals. Then it shut down the Saints, who in their next game set a record for first downs and routed Dallas.

Geno Smith has been a revelation at quarterback in some weeks, and a rookie bust in others. That kind of up-and-down performance can be expected from a first-year QB, of course, and the rest of the roster needs to come through when Smith hasn’t. Sometimes, that has worked for the Jets, sometimes not.

Dallas has far more talent than New York on offense — none of the Jets would start at a skill position for the Cowboys — and is not a collection of youngsters in a retooling program. That makes the Cowboys’ streakiness more confounding, although injuries to their defense have been significant.

In a division where 9-7 almost certainly will be good enough to make the playoffs, Dallas keeps coming back to a weak pack. There have been some strong performances, particularly in a 51-48 loss to Denver and a 17-3 smackdown of Philadelphia. And there have been some ugly meltdowns in defeats against San Diego and Detroit.

And then the debacle Sunday night in the Big Easy, punctuated by more injuries and some strange strategies.

Now the Cowboys have their bye, and they’d better figure things out during their week off.

“We have a chance to sit back and assess what we are doing on offense, defense and the kicking game,” coach Jason Garrett says, “and who we are doing it with, and how we are doing it, and how we can do it better.”